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>34.2. Data Types</A
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>   The columns of the information schema views use special data types
   that are defined in the information schema.  These are defined as
   simple domains over ordinary built-in types.  You should not use
   these types for work outside the information schema, but your
   applications must be prepared for them if they select from the
   information schema.
  </P
><P
>   These types are:

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><DL
><DT
><TT
CLASS="TYPE"
>cardinal_number</TT
></DT
><DD
><P
>       A nonnegative integer.
      </P
></DD
><DT
><TT
CLASS="TYPE"
>character_data</TT
></DT
><DD
><P
>       A character string (without specific maximum length).
      </P
></DD
><DT
><TT
CLASS="TYPE"
>sql_identifier</TT
></DT
><DD
><P
>       A character string.  This type is used for SQL identifiers, the
       type <TT
CLASS="TYPE"
>character_data</TT
> is used for any other kind of
       text data.
      </P
></DD
><DT
><TT
CLASS="TYPE"
>time_stamp</TT
></DT
><DD
><P
>       A domain over the type <TT
CLASS="TYPE"
>timestamp with time zone</TT
>
      </P
></DD
><DT
><TT
CLASS="TYPE"
>yes_or_no</TT
></DT
><DD
><P
>       A character string domain that contains
       either <TT
CLASS="LITERAL"
>YES</TT
> or <TT
CLASS="LITERAL"
>NO</TT
>.  This
       is used to represent Boolean (true/false) data in the
       information schema.  (The information schema was invented
       before the type <TT
CLASS="TYPE"
>boolean</TT
> was added to the SQL
       standard, so this convention is necessary to keep the
       information schema backward compatible.)
      </P
></DD
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   Every column in the information schema has one of these five types.
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